The prior art includes grasses that have been mutated such that flowering and production of inflorescences do not occur. These grasses, however, exhibit other unwanted characteristics such as dwarfism, leaf discoloration, root failure, and the like. The phrase “genetically modified” as used herein does not include chemical or irradiation mutagenesis, nor standard hybridization techniques that produce sterile progeny. For example, transformation with a nucleic acid to produce an alteration in the plant's genetic material is within the scope of the invention.
The prior art also includes grasses that have been treated with chemicals or phytohormones to inhibit flowering and production of inflorescences. But genetic modification in accordance with the present invention results in a change in heritable traits and does not require such treatment. Change in one or more characteristics of a genetically modified grass may be at least partially reversed by treatment with a phytohormone.
Additionally, dramatic delay of flowering has been shown in other monocots. In wheat, flowering was inhibited using a gibberellin-degrading enzyme. This wheat, however, evidenced certain deleterious side effects such as dwarfism when in the non-flowering phase. The present invention avoids these deleterious side effects.
Although inhibition of flowering in grasses is considered to be a trait of high agronomic value, we are unaware of any demonstration in the prior art that genetic modification of grass can result in a non-flowering phenotype. The present invention has a number of significant advantages both for grasses bred for forage as well as grasses bred for amenity purposes. These advantages can be summarised as follows:                As a consequence of an extended vegetative growth phase, biomass will be generated continuously in the form of leaf material, which means a significant increase of the yield of well-digestible organic matter.        The loss of nutritional quality of the crop as a consequence of the formation of strongly lignified inflorescences as well as seeds is prevented. The percentage of digestible organic matter of a non-flowering grass is estimated to be about 80% during the whole season whereas this percentage is estimated to be about 60% for a non-genetically modified flowering grass. This reduction in nutritional value is prevented by the present invention and the resulting increase in yield allows a farmer to significantly lower the use of feed additives and thereby minimise the overall emission of minerals into the environment.        Amenity grasses are improved in appearance and functional properties due to increased tillering and the absence or reduction of inflorescences.        Pollen development is blocked by a male-sterile phenotype such as inhibition of flowering. Therefore, as an additional benefit of the present invention, there is no production and spread of pollen. The environment is protected thereby from the putative risk of dissemination of traits conferred by transgenes (e.g., like herbicide resistance) to other plant species. Furthermore, allergy sufferers are protected from aggravation of their hayfever by this blockage.        
Ectopic expression of AtH1, a gene encoding a homeotic transcription factor involved in the pathway for phytochrome B signal transduction, in the dicot plants Arabidopis and tobacco resulted in a delayed flowering phenotype. The phenotype could be reversed to flowering by exogenous application of gibberellic acid (see Intl. Patent Appln. No. PCT/IB98/00821 published as WO 98/51800).
In contrast, the mechanism that controls the transition to flowering in grasses is currently unknown and persons skilled in the art had no reasonable expectation that the function of the AtH1 gene would be conserved in monocot species. Thus, the inhibition of flowering in grasses and the switch from vegetative to generative growth, instead of mere delay in flowering, was unexpected.